Shaped absorbent article and method of manufacturing the same

ABSTRACT

A flexible absorbent article such as a nappy or a sanitary pad having an absorbent core and a three-dimensional shape. The absorbent article includes a thermoformed layer formed integrally therewith which substantially maintains said three-dimensional shape. The invention also relates to a method for manufacture of the same. The cost of production of three-dimensional absorbent products can thereby be significantly reduced and more complicated shapes can be obtained.

FIELD OF THE INVENTION

The present invention relates to a flexible absorbent article, having aplurality of layers, an absorbent core, and a thermoformed layer formedintegrally therewith to maintain the absorbent article in athree-dimensional shape defining an open volume. The invention alsorelates to a method of producing such an article.

More particularly, the invention relates to absorbent articles such asabsorbent garments or sanitary pads.

BACKGROUND ART

Flexible absorbent articles of the aforementioned type are known in thefield of sanitary pads for example. An example of such a sanitary pad issold under the trademark SERENITY® and is a sanitary pad which, in therelaxed state, has a U-shaped or V-shaped appearance when viewed fromthe side in order that the pad fits more closely to the contours of thebody at the point of application. The sanitary pad has a multi-layerabsorbent core with or without SAP (super absorbent polymer), which isenclosed between an impervious back sheet layer and a porous top sheetlayer. The back sheet layer (comprising a foamed polymer layer) and thetop sheet layer are attached to each other at their respectiveperipheries with the top sheet layer in a stretched state. Since the topsheet layer is in a stretched state when attached to the foamed polymerlayer, it will thus ensure that the sanitary pad has a three-dimensionalshape defining an open volume therewithin when in the relaxed state.

Clearly, the production operation for such a sanitary pad is quitecomplicated due to the need to stretch one layer and hold it in thestretched position whilst applying and attaching a further layer to it.Due to the fact that an economic production must be achieved, some shaperestrictions on the product will also occur due to the manner ofstretching which must not be too intricate.

Thus the invention seeks to overcome said complications by providing anarticle which can be manufactured substantially without stretching butwhich has a three-dimensional shape defining an open volume therewithin,which can be varied within wide limits. The invention also seeks toprovide a corresponding method for manufacturing said product.

SUMMARY OF THE INVENTION

The aforementioned object is solved by an article having a plurality oflayers, an absorbent core, and a thermoformed layer formed integrallytherewith to maintain the absorbent article in a three-dimensional shapedefining an open volume. Similarly, the method of producing an absorbentarticle including a plurality of layers including an absorbent core byadding a thermoformable net layer to one of the plurality of layers andapplying heat ton one of the layers and the thermoformable net layerwhile the device is in a predetermined shape so as to thermoform thearticle into the predetermined shape is also described. The flexibleabsorbent article is preferably a sanitary pad or an absorbent garment,such as a nappy, the flexible absorbent article preferably has a corelocated between a backing sheet and a top sheet, has a core locatedbetween a backing sheet and a top sheet and a thermoformed layer betweenthe back sheet and the top sheet, wherein the thermoformed layer islocated with the absorbent member or wherein the thermoformed member isintegral with the back sheet.

By using a thermoformable layer in the mariner defined, the article canbe manufactured more easily and in a wider variety of shapes which aresuitable for differing applications.

The invention can also be used for absorbent products designed to have acurvature in more than one direction, e.g. saddle-shaped products (whichoffer a better fit to the body) such as saddle-shaped sanitary pads forexample.

By the term "thermoformable layer" as used in the claims and thefollowing description is meant a layer which comprises a material, suchas EVA (ethylene vinyl acetate) for example, which can be made to assumea predetermined shape in the cold state (e.g. at room temperature). Thelayer must then be able Lo substantially maintain this shape after beingheated to a sufficient temperature (typically a temperature between 85°C. and 130° C.) for a sufficient time (e.g. between 5 to 40 seconds) andsubsequently cooled (naturally or otherwise) whilst being restrained insaid particular shape. Such a layer will preferably be in the form of anet of longitudinal and transverse crossing threads or fibres, but mayalso be in the form of a layer of particles (powder, granules or fibres)of said material arranged so as to provide a stable but flexiblestructure when thermoformed. Other forms of the thermoformable layer arealso imaginable.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to theaccompanying drawings in which:

FIG. 1 shows a sectional side view of a sanitary pad during an initialstage of production of an article in accordance with the invention withthe thermoformable layer positioned between the back sheet and theabsorbent core;

FIG. 2 shows a sectional side view similar to that of FIG. 1, but withthe thermoformable layer positioned within the absorbent core;

FIG. 3 shows a sectional side view similar to that of FIG. 1, but withthe thermoformable layer placed on the outer side of the backing sheet;

FIG. 4 shows a plan view of a typical sanitary pad shape with zonesdenoting where said thermoformable layer can be placed;

FIG. 5 shows a sectional side view of a sanitary pad made in accordancewith the invention starting from the initial stage as shown in FIG. 1,and

FIG. 6 shows a perspective view of a nappy made in accordance with thepresent invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The absorbent article according to the present invention is shown in afirst embodiment in FIG. 1 having the form of a sanitary pad 1 forfemale use. The view in FIG. 1 however does not depict the finalarticle, but instead merely shows an intermediate stage of production ofsaid sanitary pad, the final product of FIG. 1 being shown in FIG. 5.

In the embodiment shown, the sanitary pad 1 comprises a top sheet 3which is designed to be in contact with the body and which is thusporous and normally very thin. A back sheet 4 is also provided and thisis normally an impervious sheet which serves to protect the wearer'sclothes from staining from fluids which are passed from the body,through the porous top sheet 3 and into the absorbent core 2.

In the depicted embodiment the absorbent core 2 is a relatively thickcore made from cellulosic pulp possibly containing SAP. However, thinnertypes of core and/or sanitary pads may also be used with this inventionwith or without a separate top sheet or backing sheet.

Before the top sheet layer 3 and the back sheet layer 4 are joinedtogether at the periphery, a layer of thermoformable material 5 isplaced on the inner surface of the backing sheet. The layer may belaminated to the backing sheet in a previous process, for example by theapplication of heat, or the layer may be added separately to the backsheet layer before application of the absorbent core 2 and held in placeby the applied core 2. In order to function satisfactorily thethermoformable layer must however be integrated into the structure ofthe article in some way either before or after thermoforming.

The back sheet layer and the top sheet layers can be of known type. Thethermoformable layer 5 is preferably in the form of a net of e.g. EVAhaving a small mesh size (e.g. 3×3 mm) which thus results in a net whichis flexible yet sufficiently rigid to allow ease of handling.

The embodiment shown in FIG. 2 differs from that in FIG. 1 only in thatthe thermoformable layer 5 is positioned in the body of the absorbentcore 2. Such positioning may occur by the layer being placed between twoseparate layers of the absorbent core which are superposed, or by thenet being added during mat-building (known per se, see e.g. themat-building/mat-forming method disclosed in e.g. EP-A-0 369 974) of theabsorbent core itself.

As shown in the figure, the outer edges of the thermoformable layer arewithin the outer boundaries of the absorbent core 2 by a small margin ateither end. This is however not a requirement and the layer 5 may extendup to or even beyond the edges of the absorbent core 2.

In the embodiment shown in FIG. 3, the thermoformable layer has beenattached to the underside of the back sheet 4, in which position it willbe easiest to thermoform into the final product by the effect of heat.Additionally, since the outer side of the back sheet is not in contactwith the body, no discomfort from the thermoformed layer will occur.Lamination of the layer 5 to the back sheet layer 4 by suitable means ispreferable in this embodiment since this allows the backing sheet to behandled easily.

Whilst the thermoformable layer 5 has been shown as a single layer, thethermoformable layer may be constituted by two or more layers (notshown) which are separated from each other. For example, a single layerof thermoformable net may be attached on either side of the back sheetlayer.

Additionally the back sheet layer may be a laminate structure with aplurality of layers, in which case the thermoformable layer may bepositioned within the layers and held in place between the layers.

FIG. 4 shows a plan view of a typical sanitary pad 6 shape. within theouter boundary 9 of the sanitary pad, taco zones 7 and 8 one depicted.These zones defile examples of the extent of the area of thethermoformable layer. Thus, in order to achieve a shape as in FIG. 5having (in a side view) only one main curved portion 10 defining theopen volume, it may be sufficient to apply the thermoformable layer 5 toa small area such as zone 8 for example. A larger zone 7 might howeverbe required if it is desired to modify the shape of the flat articleover a larger area or at the edges. The area of the zone is thus amatter of choice according to the circumstances prevailing and the exactsize required can easily be determined.

The view shown in FIG. 5 is the same as that in FIG. 1 except that thethermoformable layer 5 has been thermoformed by the application of heatand a restraining force so as to assume the bowed shape desired. Sincethe thermoformed layer is integrated into the structure of the absorbentarticle, its bowed shape is also transferred to the whole of thearticle.

The method of production of the article may vary. However, consideringthe example of FIG. 1 and FIG. 5, the thermoformable layer 5 may beadded to the back sheet 4 and then the combined back sheet layer 4 andlayer 5 moved to a further station in which the absorbent core 2 isplaced thereon. A top sheet 3 is then added which is then sealed aroundits edge 11 to the layer 4. All this may occur in the flat state of thearticle and may be an in-line procedure with a plurality of articlesstill joined together.

The article, or joined articles, is/are then transferred to athermoforming station in which the article is made to assume apredetermined three-dimensional shape by being placed onto or into amale or female mould for example. Heat is then applied for a specifiedtime (for example as indicated previously above) by appropriate meansand the article then allowed to cool naturally or by forced cooling.

Once cooled, the thermoformable layer will have been thermoformed andthus substantially maintain the shape which it assumed whilst in themould. Due to its integration between the layers 2 and 4, the wholearticle is thus maintained substantially in the new shape.

Clearly for such absorbent articles it is important that flexibility ismaintained in order to adapt to different body shapes and to accommodatemovement. Thus the thermoformable material must still be adequatelyflexible after thermoforming.

Thus, although a three-dimensional article has been formed it has notbeen necessary to stretch any of the layers and hold them in placewhilst a further layer is attached. Instead the layers merely need to beconstrained in a particular shape whilst heat is applied. Where itproves beneficial to integrate the layer 5 into the core 2, such as inFIG. 2, the further advantage is provided that the mat-building step ofthe absorbent core can still be carried out in the flat condition.

In certain cases it may be desirable to only adapt the shape of one ofthe layers (embodiment not depicted). Such a case might be where it isdesirable to form only the back sheet layer into a dished form in a waywhich allows it to partially enclose the absorbent core 2. This can beachieved by separate thermoforming of the thermoformable layer inconjunction with the backing sheet by itself, with only subsequentaddition of the absorbent core and top sheet. Alternatively the edgeregions of the backing sheet might be thermoformed whilst the back sheetlayer is held in a mould of some type to keep the remainder flat.

FIG. 6 shows a further product to which this technology may be applied.Nappies or diapers 13 for infants or adults of the basic type as in FIG.6, but having a flat form, are traditionally made by machinery whichapplies seams in two different directions, one of these being opposed tothe direction of travel in the machinery. Various webs and seals areoften also applied to obtain a type of three-dimensional structure whenthe nappy is folded out. However by use of the thermoformable layer in amanner according to the invention a more precise or complicated shapecan be given to the nappy and a shape which is substantially maintainedin the relaxed state which would allow it to perform its variousfunctions more efficiently and possibly also with reduced materials. Forexample, the shape shown in FIG. 6 may easily be achieved bythermoforming a layer 5 in said nappy to give the required curvature.The leg elastics 12 are still present and these merely assist adaptationto the user's legs during all movements. Similarly waist elastic mayalso be present.

Shaped incontinence protection pads or chassis of large or small typemay also be formed in a similar way to that described above.

The invention is not restricted to the embodiments described above butmay be varied widely within the scope of the appended claims.

I claim:
 1. Flexible absorbent article for use in absorbing bodilyfluids, said article comprising:a plurality of layers including anabsorbent core, wherein one or more of said layers has athree-dimensional shape defining an open volume therewithin, and athermoformed layer formed integrally with said plurality of layers, saidthermoformed layer substantially maintaining said one or more layers insaid three-dimensional shape, wherein said thermoformed layer is in theform of a net which is integrally thermoformed with said one or morelayers.
 2. The flexible absorbent article according to claim 1, whereinsaid article is a sanitary pad.
 3. The flexible absorbent articleaccording to claim 1, wherein said article is an absorbent garment. 4.The flexible absorbent article according to claim 1, wherein theabsorbent core is located between a backing sheet layer and a top sheetlayer and said three-dimensional shape is given to the backing sheetlayer so as to form a dished carrier for the remaining layers.
 5. Theflexible absorbent article according to claim 1, wherein saidthree-dimensional shape is provided in all layers of the article.
 6. Theflexible absorbent article according to claim 1, wherein the absorbentcore is located between a backing sheet layer and a top sheet layer andin that said thermoformed layer is located at a position between thebacking sheet layer and the top sheet layer.
 7. The flexible absorbentarticle according to claim 1, wherein said thermoformed layer ispositioned within said absorbent core.
 8. The flexible absorbent articleaccording to claim 4, wherein said thermoformed layer is integral withsaid backing sheet layer.
 9. The flexible absorbent article according toclaim 3, wherein said article is a diaper for infants or adults.
 10. Theflexible absorbent article according to claim 1, wherein said netincludes longitudinal and transverse crossing threads or fibers. 11.Method of manufacture of an absorbent article comprising a plurality oflayers including an absorbent core, said method comprising:adding athermoformable layer to one of said plurality of layers either before,during or after the manufacture of said one of said plurality of layers,wherein said one of said plurality of layers is made to assume apredetermined three-dimensional shape defining an open volumetherewithin, and wherein said thermoformable layer is in the form of anet; and applying heat to said one of said plurality of layers and saidthermoformable net layer whilst said one of said plurality of layers andsaid thermoformable net layer are in said predetermined shape so as tothermoform them substantially in accordance with said predeterminedshape.
 12. The method of manufacture of an absorbent article accordingto claim 11, wherein said one of said plurality of layers is made toassume said three-dimensional shape initially by being placed onto, orinto, a mold.
 13. The method of manufacture of an absorbent articleaccording to claim 11, wherein said absorbent core comprises a mat-builtcore of cellulosic fibres, and said thermoformable net layer is addedduring mat-building so as to be fully integrated into said absorbentcore.
 14. The method of manufacture of an absorbent article according toclaim 11, wherein said net is formed by longitudinal and transversecrossing threads or fibers.